it is probably the seals between the camshaft bays and the top cover, a DIY job if you have the right torque keys. Its a common failure on TS engines, not causing any problems if the oil does not get too high in the plug holes.
Just trawling through old stuff to see if I can find somehting similar to my problem. Is the leak around the cam shaft seal known about on the JTS engine as well as the TS?? I have evidence of lots (1/2 to 1 ltr) of oil around the plug recesses and I seem to be using 1 ltr per 500 miles!!